Proper amount of solar panels needed to charge batteries

When dealing in watts and watt-hours, it helps to get your math right if you compute a single unit's capacity, then simply multiply by the number of units. E.G. Go 115AH x 12 (not 24) volts to get 1380 watt-hours per battery, then multiply by the number of batteries, 1380WH x 4 = 5520WH whole pack.

I have no idea where you got 54V for 6 ra-220 panels in series (not parallel). You seem to be assuming 9V per panel, at 30A, = 270 watts per panel. See how much nicer "per unit" works? It's now obvious something is wrong with the math, since these panels are only rated at 220-230W. 225W x 6 = 1350W, but that's perfect conditions.

For general design, focus on the watts. The MPPT controller will sort out the volts and amps. However, you do need to make sure the "open circuit" voltage of the panels is appropriate for the MPPT controller.

Also, don't plan to bottom out the batteries if you're buying lead-acid. They are happiest when they never drop below 70% charge (i.e. only using the top 30% of charge in the battery). Dropping below 50% should be uncommon, and draining dead should be rare. Doing so prematurely ages the battery.

If you want a battery you can frequently deep discharge and otherwise abuse, look at Nickel-Iron or Nickel-Cadmium (not NiMH).

I’ve not seen a golf cart battery that was only 20AH , the 215 number sounds plausible so you would have 215 Ah at 12v with 2 batteries.

Are you sure you have your numbers correct? My guess would be you have an inverter that outputs 300w at 120, to do this it would draw ~25 amps from the batteries (the draw would be more because of losses in converting 12vdc to 120v ac).

If you want your batteries to last don’t discharge past 50% but golf cart batteries “deep cycle “ can go down to 80% but will only last a couple of years. Using 50% this would provide around 4.3 hours of run time from the batteries alone 25amps or 107.5 ah used , your run time would be extended by adding the solar if in full sun your total run time could be 11.8 hours as you would only be drawing ~9 amps from the batteries but you know your not going to have full sun and this would leave the batteries in a depleted condition or at 50%. If you provide more information on your inverter we may be able to provide better examples.